Many modern computing devices employ graphic user interfaces shown on a display to provide user interaction. The displays can be one of many different peripheral elements controlled by a computer through a communication bus. The core element of a computer is the central processing unit (CPU). The CPU is a stored-program machine that executes software programs stored in memory devices connected to the CPU through the communication bus. Typically, the communication bus also connects the CPU to other computer peripherals, including for example disk drives, keyboards, and a pointing device such as a touch screen, mouse, joystick, touch pad, or track ball. Sometimes the peripherals are connected through single-connection ports, such as the universal serial bus (USB). Some connection ports and buses can connect serially or in parallel to multiple devices.
The conventional architecture for computers is very adaptable but, because each computing element typically performs a single function and is connected to other computing elements through single communication paths, the conventional computer architecture is subject to performance limitations imposed by the performance of a single component, for example memory, memory access rates, a communication bus or port, or the speed of the central processing unit. Parallel computers have been designed to deal with the problem of limited CPU performance, memory access rates, and the interconnection between memory and the CPU. Some parallel computers employ a plurality of CPUs, each with its own memory, connected through communication ports, either point-to-point, or through a global access bus. Other parallel computers employ multiple CPUs and a large, globally accessible memory with a high-speed, multi-connection access bus. These designs address the problem of CPU performance and memory access.
However, computers are increasingly employed in user-interactive, portable, graphic, display-and-image-centric applications, such as internet access, mobile communications, and entertainment such as video gaming and watching video sequences. These applications require a very high bandwidth to the display in a very small, thin, flexible, low-power form factor suitable for user and environmental interaction. Conventional computer architecture designs are not well suited to such applications. Specifically, most traditional designs employ a graphics processor, which can decode and decompress digital signals to a rasterized signal or render graphical objects to a rasterized signal. This rasterized signal is then provided to the display over a high-bandwidth connection. However, this high-bandwidth connection can be expensive and is often limited to a few megabits per second, making it difficult to render images to displays having more than a few million pixels at the required refresh rates.
Flat-panel display devices, for example plasma displays, liquid crystal displays, and area-emissive light-emitting diode (such as organic light-emitting diode or OLED) displays, are widely used in conjunction with computing devices, in portable electronic devices, and for entertainment devices such as televisions. Such displays typically employ a plurality of pixels distributed over a substrate in a display area to display images. Each pixel incorporates several, differently colored light-emitting elements commonly referred to as sub-pixels, typically emitting red, green, and blue light, to represent each image element. As used herein, pixels and sub-pixels are not distinguished and refer to a single light-emitting element. A controller external to the display area drives circuitry that activates each of the pixels, either with active-matrix or passive-matrix control. The controller can include multiple chips, for example as taught in U.S. Pat. Nos. 7,361,939 and 6,582,980. The controller chips can be located on the display substrate, as disclosed in U.S. Patent Application 2005/0073260. Active-matrix circuits include thin-film electronic circuitry on the flat-panel display substrate in the display area constructed using high temperature processes. Passive-matrix circuits employ controllers external to the display and are limited to relatively small displays. An alternative pixel-control method using crystalline silicon substrates used for driving LCD displays is described in U.S. Patent Application Publication No. 2006/0055864. Such flat-panel displays and control methods are limited in the data rates at which the pixels can be controlled by the controller or the communication path between the controller and the pixels.
WO2010046638 describes active matrix devices with chiplets connected in a logical chain.
Many portable laptop computers integrate displays and computing elements in a folding clamshell, and it is known to integrate a display and computer in a common housing (see, e.g. U.S. Patent Publication 2008/0024971) but these systems are constructed on rigid substrates and are thicker and heavier than can be desired. While flat-panel display devices, particularly OLED displays, can be quite thin, it is difficult to build flat-panel displays on flexible structures. Flexible substrates are typically limited to low-temperature processes and require additional processing to construct conventional active-matrix thin-film electronic circuits.
It is known to affix conventional, packaged integrated circuits on a display substrate outside the display area to reduce external parts count and the number of physically separate system elements. A thin form factor is especially important in displays such as OLED displays which can be formed with a thickness of a few millimeters or less. In such displays, electronics packaged outside the display can require a thickness several times the thickness of the display and therefore increase the total display thickness.
Externally accessible circuits that measure OLED pixel performance are known in the prior art. The performance measurements are then used to provide compensation, for example with an external lookup table that processes an image before the image is transferred to a display. These compensation designs suffer from the same bandwidth limitations as conventional display designs and also increase the computing needs for external display controllers. Sophisticated current-controlled pixel-driving circuits are also known, as are circuits that detect emitted light and adjust the driving circuit to provide the desired amount of light. These pixel-control circuits are useful for ensuring that a display emits the desired amount of light specified by a pixel value but do not actually modify the image content as specified by the image pixel values.
There is a need, therefore, for a computer and display architecture that provides a digital display device having improved display bandwidth, a reduced need for external image processing and bandwidth, a thin and flexible form factor, reduced power, a high level of integration, and interactivity.